fontheight is a tool that provides recommendations on setting font vertical metrics based on shaped words.
Vertical metrics frequently decide clipping boundaries, but are not used consistently across platforms: e.g. Windows uses OS/2 WinAscent/WinDescent, whereas for system fonts Android uses TypoAscent/TypoDescent and a combination of custom heuristics.
It is often desirable to derive metrics from shaped words as opposed to individual glyphs, as words may reach greater extents:
Early versions of this specification suggested that the usWinAscent value be computed as the yMax for all characters in the Windows “ANSI” character set. For new fonts, the value should be determined based on the primary languages the font is designed to support, and should take into consideration additional height that could be required to accommodate tall glyphs or mark positioning.
⬆️ OS/2 — OS/2 and Windows Metrics Table, OpenType Specification 1.9.1
For this reason, vertical metrics must be chosen with a combination of design (e.g. aesthetic, legibility) and engineering (e.g. clipping) considerations in mind.
For the latter, fontheight evaluates the extents of a corpus of shaped text across each writing system that a font intends to support.
Fontheight comes in three flavours:
- A commandline tool (
fontheight) - A basic Python API (
fontheight-wheel) - A Rust library (
fontheight-core)
Currently, both installation methods involve compiling fontheight from its source code, meaning you need to have a Rust toolchain installed and cargo available in your terminal.
If you're new to Rust, check out https://www.rust-lang.org/tools/install for instructions on getting it installed and configured.
You only need a stable compiler for Font Height's crates.
From GitHub:
STATIC_LANG_WORD_LISTS_LOCAL=1 cargo install --locked --git https://github.com/googlefonts/fontheight fontheightstatic-lang-word-lists requires network access):
cargo install --locked fontheightUsage: fontheight [OPTIONS] [FONT_PATH]...
Arguments:
[FONT_PATH]... The TTF(s) to analyze
Options:
-n, --results <RESULTS> The number of words to log [default: 5]
-k, --words <WORDS_PER_LIST> The number of words from each list to test [default: 25]
-h, --help Print help
-V, --version Print version
Most of the word list shipped with fontheight are sorted by greatest vertical extremes to try and help reduce the number of words which need to be checked to produce a useful report.
However, not all word lists have been sorted at this time, and so for greater reliability you may wish to use a greater value for --words, or use --all.
Unsorted word lists
- DiffenatorBopomofo
- DiffenatorGeorgian
- DiffenatorHiragana
- DiffenatorJapanese
- DiffenatorKatakana
- DiffenatorThanaa
- DiffenatorTifinagh
Sorted word lists (and fonts used in sorting)
Sorted DiffenatorAdlam based on:
- NotoSansAdlam[wght].ttf
- NotoSansAdlamUnjoined[wght].ttf
Sorted DiffenatorArabic based on:
- NotoKufiArabic[wght].ttf
- NotoNaskhArabic[wght].ttf
- NotoSansArabic[wdth,wght].ttf
Sorted DiffenatorArmenian based on:
- NotoSansArmenian[wdth,wght].ttf
- NotoSerifArmenian[wdth,wght].ttf
Sorted DiffenatorAvestan based on:
- NotoSansAvestan-Regular.ttf
Sorted DiffenatorBengali based on:
- NotoSansBengali[wdth,wght].ttf
- NotoSerifBengali[wdth,wght].ttf
Sorted DiffenatorCanadian_Aboriginal based on:
- NotoSansCanadianAboriginal[wght].ttf
Sorted DiffenatorChakma based on:
- NotoSansChakma-Regular.ttf
Sorted DiffenatorCherokee based on:
- NotoSansCherokee[wght].ttf
Sorted DiffenatorCommon based on:
- NotoSansLGC[wdth,wght].ttf
- NotoSansMonoLGC[wdth,wght].ttf
- NotoSerifLGC[wdth,wght].ttf
Sorted DiffenatorCyrillic based on:
- NotoSansLGC[wdth,wght].ttf
- NotoSansMonoLGC[wdth,wght].ttf
- NotoSerifLGC[wdth,wght].ttf
Sorted DiffenatorDevanagari based on:
- NotoSansDevanagari[wdth,wght].ttf
- NotoSerifDevanagari[wdth,wght].ttf
Sorted DiffenatorEthiopic based on:
- NotoSansEthiopic[wdth,wght].ttf
- NotoSerifEthiopic[wdth,wght].ttf
Sorted DiffenatorGreek based on:
- NotoSansLGC[wdth,wght].ttf
- NotoSansMonoLGC[wdth,wght].ttf
- NotoSerifLGC[wdth,wght].ttf
Sorted DiffenatorGujarati based on:
- NotoSansGujarati[wdth,wght].ttf
- NotoSerifGujarati[wght].ttf
Sorted DiffenatorGurmukhi based on:
- NotoSansGurmukhi[wdth,wght].ttf
- NotoSerifGurmukhi[wght].ttf
Sorted DiffenatorHebrew based on:
- NotoRashiHebrew[wght].ttf
- NotoSansHebrew[wdth,wght].ttf
- NotoSerifHebrew[wdth,wght].ttf
Sorted DiffenatorKhmer based on:
- NotoSansKhmer[wdth,wght].ttf
- NotoSerifKhmer[wdth,wght].ttf
Sorted DiffenatorLao based on:
- NotoSansLao[wdth,wght].ttf
- NotoSansLaoLooped[wdth,wght].ttf
- NotoSerifLao[wdth,wght].ttf
Sorted DiffenatorLatin based on:
- NotoSansLGC[wdth,wght].ttf
- NotoSansMonoLGC[wdth,wght].ttf
- NotoSerifLGC[wdth,wght].ttf
Sorted DiffenatorLisu based on:
- NotoSansLisu[wght].ttf
Sorted DiffenatorMalayalam based on:
- NotoSansMalayalam[wdth,wght].ttf
- NotoSerifMalayalam[wght].ttf
Sorted DiffenatorMongolian based on:
- NotoSansMongolian-Regular.ttf
Sorted DiffenatorMyanmar based on:
- NotoSansMyanmar[wdth,wght].ttf
- NotoSerifMyanmar[wdth,wght].ttf
Sorted DiffenatorOl_Chiki based on:
- NotoSansOlChiki[wght].ttf
Sorted DiffenatorOriya based on:
- NotoSansOriya[wdth,wght].ttf
- NotoSerifOriya[wght].ttf
Sorted DiffenatorOsage based on:
- NotoSansOsage-Regular.ttf
Sorted DiffenatorSinhala based on:
- NotoSansSinhala[wdth,wght].ttf
- NotoSerifSinhala[wdth,wght].ttf
Sorted DiffenatorSyriac based on:
- NotoSansSyriac[wght].ttf
- NotoSansSyriacEastern[wght].ttf
- NotoSansSyriacWestern[wght].ttf
Sorted DiffenatorTamil based on:
- NotoSansTamil[wdth,wght].ttf
- NotoSerifTamil[wdth,wght].ttf
Sorted DiffenatorTelugu based on:
- NotoSansTelugu[wdth,wght].ttf
- NotoSerifTelugu[wght].ttf
Sorted DiffenatorThai based on:
- NotoSansThai[wdth,wght].ttf
- NotoSansThaiLooped[wdth,wght].ttf
- NotoSerifThai[wdth,wght].ttf
Sorted DiffenatorTibetan based on:
- NotoSerifTibetan[wght].ttf
Sorted DiffenatorVai based on:
- NotoSansVai-Regular.ttf
The API will be available under the package libfontheight and then is imported as fontheight
See the method signatures & data types below, approximately written in Python. k_words is equivalent to --words in the CLI, and n_exemplars is equivalent to -n/--results
import fontheight
# Entrypoints
fontheight.get_min_max_extremes_from(path: os.pathLike, k_words: int, n_exemplars: int) -> list[fontheight.Report]
fontheight.get_min_max_extremes(font_bytes: bytes, k_words: int, n_exemplars: int) -> list[fontheight.Report]
# Returned data types
@dataclass(frozen=True)
class fontheight.Report:
location: dict[str, float]
word_list_name: str
exemplars: fontheight.Exemplars
@dataclass(frozen=True)
class fontheight.Exemplars:
lowest: list[fontheight.WordExtremes] # sorted, lowest lows first
highest: list[fontheight.WordExtremes] # sorted, highest highs first
@dataclass(frozen=True)
class fontheight.WordExtremes:
word: str
lowest: float
highest: floatfontheight-core
For documentation, please refer to docs.rs